The disclosures herein relate generally to orthopedic implant systems and more particularly to an anterior or posterior referencing instrument including an anterior femoral cutting guide and a distal femoral cutting guide.
There are many problems encountered by orthopedic surgeons when attempting to properly size and reset the distal femoral articulating surfaces in preparation for total knee arthroplasty. The intramedullary canal is located for proper centering of an intramedullary rod to be inserted therein. Anterior or posterior referencing are used to properly establish cutting planes for receiving a properly sized femoral reconstruction component. In anterior referencing, anterior-posterior placement of the femoral component is based on the anterior cortex as a primary point of reference. In posterior referencing, anterior-posterior placement of the femoral component is based on the posterior femoral condyles as a primary point of reference.
Numerous approaches have been taken to achieve accurate sizing for a knee prosthesis. U.S. Pat. No. 5,417,694 and U.S. Pat. No. 5,569,261, each disclose a distal femoral cutting instrument which includes an intramedullary rod for referencing the patient's intramedullary canal. A valgus block with a flat reference surface mounts to the intramedullary rod at a bore of the valgus block. The bore of the block has a slant with respect to the flat reference surface on the valgus block. The reference surface defines a line that is normal to the mechanical axis of the patient while the bore of the valgus block tracks the patient's biomechanical axis. A distal femoral cutting block removably attaches to the valgus block and provides a flat cutting guide surface for shaping the patient's distal femur. The valgus block, intramedullary rod, and a stylus are removed as a unit before shaping of the distal femur. An indexing system includes a gauge having a series of openings corresponding to "anterior" referencing and to "posterior" referencing. During anterior referencing, the gauge allows the surgeon to select the next smaller size prosthesis if the size falls in between available sizes. In posterior referencing, the gauge allows the surgeon to select the next larger size prosthesis if the gauge measures a size that falls in between available sizes.
In U.S. Pat. No. 5,486,178, a femoral preparation instrumentation system and method employs a multi-purpose sizing guide for placement at the distal femur, secured to an intramedullary alignment rod seated within the femur, enabling the determination of the appropriate size for the femoral knee prosthesis to be implanted and the setting of the axial rotational position of the femoral knee prosthesis, and providing for the accomplishment of preliminary posterior condylar cuts and the location of a distal femoral resection guide at the distal femur, while the sizing guide remains in place at the distal femur.
U.S. Pat. No. 5,624,444 discloses a set of instruments and method for use in knee replacement surgery, specifically to make the necessary femoral resections. The set of instruments allows the necessary femoral resections to be performed with fewer instruments, and with fewer necessary steps for the surgeon to take. The set of instruments includes a three-dimensional jig which references the anterior and posterior femoral condyles to allow determinations as to alignment, placement, and prosthesis size before any bone cuts are made.
U.S. Pat. No. 5,662,656 discloses instrumentation for and a method of sizing the end of a distal femur, and resecting the distal femur. An instrument body construct is provided with an instrument body and a valgus module for attachment to the instrument body. The instrument body construct has a distal aspect abutting surface with a planar face for abutting the distal aspect of a distal femur at a fixed angle to the longitudinal axis of the distal femur, a posterior aspect abutting surface with a planar face for abutting the posterior aspect of the distal femur, and a passageway therethrough. An anterior feeler gauge is provided for attachment to the instrument body construct and for contacting a portion of the anterior aspect of the distal femur to indicate the anterior-to-posterior size of the distal femur. A resection guide is provided for attachment to the instrument body construct for guiding a bone resection tool to resect the distal femur. The resection guide may have a first position for guiding the bone resection tool to perform an anterior femoral resection, and a second position for guiding the bone resection tool to perform a distal femoral resection.
In U.S. Pat. No. 5,688,279, an alignment guide for positioning a saw guide at a predetermined position on the distal femur is placed on the femur and receives an intramedullary rod inserted in the femur. The guide has an arm for coupling the saw guide block. The guide includes an intercondylar saddle that engages the intercondylar notch of the femur to align the saw guide at a predetermined position proximal to the intercondylar notch.
U.S. Pat. No. 5,688,281 discloses an intramedullary alignment guide and method for use thereof for accurately preparing and shaping the distal femur end surface to receive a knee prosthesis. The guide references the femur intramedullary canal to ensure that a distal femoral resector is properly positioned at a selected angle with respect to a patient's mechanical axis. The intramedullary alignment guide includes an opening for inserting an intramedullary rod therethrough and into the intramedullary canal of a patient. The guide includes an adjustment mechanism which allows a surgeon to quickly and easily deflect an attached distal femoral resector into a desired angular displacement with respect to the intramedullary canal. The distal femoral resector is angled with respect to the intramedullary canal so that a cut can be made in a patient's distal femur end which is perpendicular with the patient's mechanical axis. The guide can be used on patients having various anatomies, and in operations involving both the right and left legs. A slighting tool is also disclosed which allows a surgeon to externally verify that the distal femoral resector is properly aligned with the patient's mechanical axis.
Therefore, what is needed is an instrument which permits anterior and posterior referenced sizing and guide slots for making both the anterior reference femoral cut and the distal femoral cut thus providing a first and a second locating datum for subsequent use of a chamfer speed block.